There's a lot at stake on a few big, slow, brown rivers in the Deep South. The Apalachicola-Chattahoochee-Flint River Basin (ACF) is becoming the canary-in-the-coal mine for a looming East Coast water crisis. The Hanson brothers grew up in Atlanta beside the Chattahoochee River. In March 2013, they returned and paddled, together and separately, the 542 miles of the basin from its source in the Appalachian Mountains to the Gulf of Mexico. Their journey and the people they meet along the way tell the story of an endangered and essential natural resource.